WebSocket: Add simple "refresh" event.
WebSocket: Add simple "refresh" event.

This is useful for when deploying updates to allow us to restart
everyone and get them on the new code.

sim642/reddit-plugin-liveupdate,madbook/reddit-plugin-liveupdate,florenceyeun/reddit-plugin-liveupdate,florenceyeun/reddit-plugin-liveupdate,florenceyeun/reddit-plugin-liveupdate,madbook/reddit-plugin-liveupdate,sim642/reddit-plugin-liveupdate,sim642/reddit-plugin-liveupdate,madbook/reddit-plugin-liveupdate